Photodynamic therapy (PDT) is a treatment that is based upon the differential uptake by cancerous cells of photosensitizing agents, followed by irradiation of the cells to cause a photochemical reaction that is believed to generate chemically disruptive species, such as singlet oxygen. These disruptive species in turn injure the cells through reaction with cell parts, such as cellular and nuclear membranes. Photodynamic therapy has been used successfully for treating several types of cancer cells.
However, certain types of cancers, such as the very virulent pigmented melanoma, are known to be poorly responsive to photodynamic therapy (PDT) with FDA-approved photosensitizing agents such as Photofrin, a haematoporphyrin derivative (1), as well as with several second generation phototherapeutic agents (2) whose lowest energy absorption band lies in the 600-700 nm spectral range. This lack of response is generally ascribed to optical filtering of the incident light by the melanin granules, which are expressed with a particularly high frequency in this tumor type.
One avenue taken used to address this problem has been to attempt to develop and use new photosensitizing agents that have energy absorption bands deeper in the infrared region than those mentioned above. One of the difficulties in this approach has been that such new photosensitizing agents are not as effective in their generation of disruptive species once irradiated, and they require further FDA approval.
Accordingly, it is an object of the present invention to develop effective techniques whereby pigmented cancer cells may be treated by PDT, including through techniques that apply efficient and approved photosensitizing agents.
In view of the present disclosure and the practice of the present invention, other advantages of the present invention may become apparent.